There have been concerns about the stability of the nuclear test site since the September 3 test. Website 38 North said satellite imagery taken after that test appeared to show landslides atop the site that were more numerous and widespread than after the previous five tests.

The size of Saturday's tremor is smaller than that usually detected when North Korea has tested weapons.

His comments were later clarified when North Korean foreign minister, Ri Yong Ho, said it could mean that the country would test a hydrogen bomb in the Pacific Ocean.

Previous quakes from North Korea have indicated nuclear tests by the reclusive state, the most recent earlier this month. Japan and South Korea, the two closest allies of United States in the region, have claimed threat from the spree of missile tests conducted by the North.

Foreign Minister Ri Yong Ho spoke to reporters in NY, where he is attending the United Nations General Assembly.